U.S. Pat. No. 7,172,779 B2 and DE 202005006262 U1 disclose packages which offer the possibility of reclosing the package by means of locking elements formed in the lower part of the package as well as in the lid, so as to guarantee that, when part of the products has been removed, the remaining part of the products in the package will be preservable for a sufficiently long period of time. The locking elements serve to confirm, by an audible snap, that the package is reclosed and to interconnect the two package halves such that, when the upper package half is raised, the lower package half cannot detach itself from the upper one in spite of the weight of the product.
U.S. Pat. No. 7,665,281 B2 and US 2007/0138192 A1 disclose a method in the case of which the locking elements are simultaneously formed in both package halves in a work station, when both said package halves have been closed in a sealing station of a deep-drawing packaging machine so as to form a hermetically sealed package. During this deformation process, the locking elements are produced by impressing embossing means into the sidewalls of both package halves into a counter-support. This method is not suitable for very stable hard foils used as a bottom foil (product tray).
On the contrary, the foils are subjected to cold forming in the area of the locking elements and this may lead to a formation of cracks and to indefinite differences in the wall thicknesses of the individual foils. This, in turn, may lead to leakiness and, consequently, to flaws in the package.
Another drawback is the high impressing force of the embossing means required for simultaneously cold forming both foils in common.